We have previously commented (more than once) on the perception that metformin may have some value in the management of prostate cancer. A recently reported (albeit small), prospective Swiss study, has added to our knowledge in this regard.
Rothermundt et al. wanted to explore the effects of metformin in treatment of patients with castration-resistant prostate cancer (CRPC). In particular, they wanted to investigate impact of this drug on progression-free survival (PFS) and PSA doubling time in men with metastatic CRPC.
They enrolled 44 patients with progressive, metastatic CRPC into a single-arm, Phase II clinical trial during 2011. All 44 patients were treated with metformin (1 g twice daily) until disease progression. (The paper’s abstract does not tell us what other drugs these patients might also have been taking at the time.) The primary endpoint of this study was the absence of any disease progression at 12 weeks after initiation of therapy.
Here is what they found:
- 16/44 patients (36 percent) were progression-free at 12 weeks.
- 4/44 patients (9 percent) were progression-free at 24 weeks.
- 2/44 patients (5 percent) had a PSA decrease of 50 percent from baseline.
- 23/44 patients (52 percent) exhibited prolongation of their PSA doubling time.
- There was a significant change in insulin-like growth factor-1 (IGF-1) and IGF binding protein 3 from baseline to week 12.
Now this is a small, single-arm trial and, as the authors have been careful to point out in the conclusion to their original paper, as well as in a separate “Beyond the Abstract” set of comments on the UroToday web site, the clinical effect shown in this trial is “modest” at best. The authors also note that it is far too early to come to the conclusion that metformin is an appropriate form of therapy for most men with prostate cancer, but there are several other clinical trials ongoing, and we shall have to see if this “modest” effect is replicated in some of those other trials.